Computer graphics stick representation of Chlorophyll-a, the photosynthetic pigment of green plants that harnesses sunlight as energy for photosynthesis, the process that converts carbon dioxide in the air into carbohydrate. On the left of image is the heart of the chlorophyll molecule, a porphyrin ring structure which has a magnesium atom at its centre (represented by the intersection of the broken mauve lines). The magnesium atom is bonded to four nitrogen atoms that are part of four pyrrole rings. These four rings are joined by four carbon atoms to form the flat porpyhrin ring. Various other groups of atoms are attached to the outside of the ring.